Robust Self-powered Wireless Plant-monitoring Sensor System with Sap-activated Battery

Abstract

A robust self-powered wireless plant-monitoring sensor with a wide operating margin is proposed. The sensor consists of a sap-activated battery with a storage capacitor, an intermittent-power-supply circuit, and a wireless transmitter. The battery is composed of a galvanized iron nail inserted into the stem of a plant and multiple stainless-steel rods planted in the soil to enable robust operation. A sap-activated battery varies the current generation when the position of the nail inserted into the stem is changed. The battery with multiple stainless-steel rods increases the generating current and makes it possible to perform sensing operation no matter where the nail is inserted. The effectiveness of our wireless sensor system was evaluated for a tomato grown in a commercial greenhouse.